Depends on kwin!897 and kwin!959 (merged).
This commit makes use of the new hasIdenticalIcon property of the TabBox
model so that the Large Icons Task Switcher can disambiguate identical
icons. It does so by adding window thumbnails to any icons that are
identical, which makes the visual representation seen by the user no
longer identical.
If compositing is turned off, the new compositingEnabled property of the
Switcher item tells us, so we don't try to render the window thumbnail
and end up with an overlay of the same icon on top of itself
The icons in the Small Icons Task Switcher are too small for window thumbnails to be distinguishable, so they are not shown for that Task Switcher.
Here's how it looks with two Firefox Windows open:
cc @teams/vdg